1. Field of the Invention
The present invention relates to an apparatus for the transfer or conveyance of a slurry and the simultaneous densification thereof through the intermediary of vacuum pumping. Specifically, the invention pertains to an apparatus for the vacuum pumping of a slurry, particularly a zinc-containing slurry utilized in the preparation of zinc anodes for alkaline batteries, which facilitates the transfer of the slurry and the concurrent densification thereof in conjunction with the elimination of any gas bubbles which are entrapped in the slurry. Moreover, pursuant to a further aspect, the invention is also directed to the provision of a method of transferring and simultaneously densifying of a slurry while eliminating entrapped gas bubbles therefrom through the intermediary of a vacuum pumping process utilizing the apparatus of the invention.
2. Discussion of the Prior Art
An important aspect in the formation of slurries which are employed as the basic materials for the production of alkaline battery anodes, whereby such slurries generally contain primarily zinc constituents, resides in that the slurries must exhibit consistent densities essentially devoid of entrained gas bubbles in order to be able to formulate industrially and commercially acceptable battery components. This is a problem which has heretofore been inadequately solved in the technology relating to the formation of battery anode slurries.
In essence, the demands of industry necessitate that electrical batteries be able to meet and maintain specific performance standards, and in order to comply with these requisites, among other considerations, the battery anode must possess a uniform consistency and specific density and consistency throughout the material. Slurries which are formulated for the mass-production of alkaline battery anodes and which extensively contain zinc as a primary constituent, are produced through a variety of means.
The initial zinc anode slurry for the alkaline batteries is essentially produced in batch sequences; for example, through dry mixing, wet mixing, pregelling, reworking and the like, at some period in time prior to conveying or pumping the slurries to the battery cell manufacturing assembly for producing the anode constituent of the battery cells. Pumping of the slurry is implemented in timed cooperation with the slurry forming process, preferably through the use of a slurry vacuum pump apparatus. This batchwise slurry forming process sequence generally causes the presence of entrained bubbles to be encountered; for instance, such as air bubbles or other gas bubbles generated by the contacting between zinc and the metallic walls of the mixing vessels, during mixing of the slurry constituents so as to during transfer of the slurry to cell assemblies produce uneven densities in the various cells, thus adversely affecting the desired battery cell consistencies and physical characteristics. Although attempts have been made to eliminate the presence of gas or air bubbles which are entrained in the slurry batches, the elimination of bubbles and densification of the slurries prior to transfer of the battery cell producing facilities is still somewhat of being supplemented in meeting the quality standards of the alkaline storage battery manufacturing industry. For instance, among problems encountered are the formation of small bubbles (micro-bubbles) during slurry mixing and processing, the zinc to steel contact resulting in hydrogen gas bubbles, and large (macro) bubbles produced during slurry transfer. These aspects cause erratic slurry dispensing; i.e., burping and spitting when poured into the cells; variations in anode weights during dispensing, with concomitant inefficient utilization of internal battery anode space and battery characteristics and properties, rendering them commercially unusable.